JP2002261114A - Wire bonding apparatus and wire bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve highly accurate bonding by considering the absolute positional displacement of a camera and correcting the relative positional relationship between the camera and a horn. SOLUTION: This wire bonding apparatus includes a driving amount calculation unit 13 for calculating the driving amounts of a XY table 2 in correspondence with the differences between the positional displacement of the camera 9 due to changes in temperature of a first holding body 8 with respect to a fixed base 3 and the positional displacement of a capillary 7 due to changes in temperature of a second holding body 5 with respect to the fixed base 3. On the coordinate system where the camera 9 and the capillary 7 move integrally by the XY table 2, the relative positional displacement of an object 4 to be bonded, by imaging with the camera 9, which occurs by slight displacements with respect to the fixed base 3 due to each heat fluctuation of the camera 9 and the capillary 7, is calculated. By correcting moving amounts of the XY table 2 on the basis of such a calculation, the displacement of bonding positions due to heat fluctuation is dissolved, and the bonding of highly accurate positions can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus and a wire bonding method, and more particularly to a wire bonding apparatus and a wire bonding method in which a relative displacement of a capillary with respect to an object to be bonded is caused by a temperature change.

[0002]

2. Description of the Related Art In order to assemble a semiconductor device, wiring to an electrode pad of a semiconductor substrate is automatically performed. For such wiring, an automatic bonding apparatus is used. The automatic bonding device includes a horn device that applies ultrasonic waves to a bonding wire fed from a capillary. The bonding target point of the semiconductor device is monitored by a camera. Such an automatic bonding apparatus is known from Japanese Patent Application Laid-Open No. 01-161727. Such known devices include a temperature detecting means for detecting the temperature of the horn and a length change due to a thermal expansion of the horn based on a detection result of the temperature detecting means in order to perform the positioning of the bonding position with high precision. Correction means is provided for obtaining the minute and correcting a predetermined relative distance between the capillary and the camera.

If the relative displacement between the camera and the capillary due to the thermal expansion coefficient and dimensions of the holding means for holding the camera fixedly and the horn, and the temperature change from the initial setting state is not taken into consideration, the temperature of the horn is not considered. It is not possible to eliminate the cause of the positional shift due to the thermal expansion of the mechanical component due to the change, and it is not possible to correct the shift of the reference bonding position of the semiconductor element to be bonded. The prior art does not disclose any correction means based on the thermal expansion of the holding means for holding the camera, does not suggest that such correction is important, and furthermore, does not allow for the presence of thermal deformation of the bonding object at all. Not aware

It is required to correct the relative positional relationship between the camera and the horn in consideration of the absolute positional displacement of the camera. Furthermore, further improvement in the accuracy of the bonding position in consideration of the thermal expansion and contraction of the bonding object will be required for future semiconductor devices.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wire bonding apparatus for correcting a relative positional relationship between a camera and a horn in consideration of an absolute positional displacement of the camera.
Another object of the present invention is to provide a wire bonding method.
Another object of the present invention is to provide a wire bonding apparatus and a wire bonding method that realize a higher precision of a bonding position in consideration of thermal expansion and contraction of a bonding target.

[0006]

Means for solving the problem are described as follows. The technical items appearing in the expression are appended with numbers, symbols, and the like in parentheses (). The numbers, symbols, and the like are technical items that constitute at least one embodiment or a plurality of the embodiments of the present invention, in particular, the embodiments or the examples. Corresponds to the reference numerals, reference symbols, and the like assigned to the technical matters expressed in the drawings corresponding to the above. Such reference numbers and reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments or the examples.

The wire bonding apparatus according to the present invention comprises an XY table (2), a first holder (8) supported by the XY table (2), and a camera (9) held by the first holder (8). ), A second holder (5) supported by the XY table (2), a capillary (7) held by the second holder (5), and a fixing table (4) for fixing the article (4) to be bonded. 3), the displacement of the camera (9) due to the temperature change of the first holder (8) with respect to the origin of the XY table (2), and the displacement of the second holder (5) with respect to the origin of the XY table (2). A drive amount calculation unit (13) for calculating the drive amount of the XY table (2) based on the displacement of the capillary (7) caused by the temperature change. The first holder (8) and the second holder (5) are independently thermally deformed on a coordinate system in which the camera (9) and the capillary (7) move in the same body by the XY table (2). Calculate the small displacement generated at the relative position between the camera (9) and the capillary (7), and detect and
The calculated position of the bonding target product (4) is corrected. By correcting the amount of movement of the XY table (2) based on the displacement of the capillary (7) held by the second holding body (5), the displacement of the bonding position due to thermal fluctuation is eliminated, and Accurate position bonding can be realized. The relative displacement between the camera (9) and the capillary (7) due to the thermal fluctuation is detected by detecting the temperature of the holder (8) supporting the camera (9) and the temperature of the support (5) supporting the capillary (7). Can be calculated physically.

[0008] An expansion coefficient calculation unit for calculating the expansion coefficient of the bonding object (4) is further added. in this case,
The drive amount calculation unit (13) calculates the displacement of the bonding object (4) with respect to the fixed base (3) based on the expansion rate in consideration of the displacement described above. By adding the displacement of the bonding (target) point due to the expansion of the bonding target product (4) to the two displacements described above, more accurate bonding position control is possible.

[0009] The expansion rate of the product to be bonded (4)
2 points (24-1 and 24-2, or 25-1 and 25-
It is calculated based on the reference length (L) of 2) and the current length (L + ΔL) of two points (24'-1 and 24'-2 or 25'-1 and 25'-2) of the current time. obtain. If the temperature is known, the positional deviation of the local point of the bonding target product can be calculated based on the known expansion rate of the bonding target product. However, the expansion and contraction between the reference points of the bonding target product can be directly calculated by the camera (9). Measuring may allow for more accurate detection of the displacement.

[0010] A temperature detector (18) for detecting the temperature of the second holder (5) may be further added. In this case, the drive amount calculation unit (13) calculates the displacement of the capillary (7) based on the temperature. First holder (8)
A first temperature detector (16) for detecting a first temperature of the
A second temperature detector (1) for detecting a second temperature of the holder (5)
8) can be provided. In this case, the drive amount calculation unit (13) calculates the position displacement of the camera (9) as the first displacement.
The calculation is performed based on the temperature, and the displacement of the capillary (7) is calculated based on the second temperature. Also in this case, the expansion coefficient of the bonding target product (4) described above is taken into account.

[0011] The wire bonding method according to the present invention comprises:
Driving the XY table (2) to move the camera (9) supported by the first holder (8) supported by the XY table (2) with respect to the bonding target product (4); By driving (2), XY
The capillary (7) supported by the second holder (5) supported by the table (2) is moved with respect to the bonding object (4), and the bonding object (4) is imaged by the camera (9). By calculating the first positional deviation of the bonding object (4) caused by the thermal fluctuation of the first holder (8) in the coordinate system defined by the camera (9), the second holder Calculating the second displacement of the capillary (7) caused by the thermal fluctuation of (5);
The XY table (2) is driven based on the positional deviation and the second positional deviation.

The object to be bonded (4) is imaged by the camera (9), and the distance between the two points of the object to be bonded (4) is calculated in the coordinate system defined by the camera (9) to thereby obtain the object to be bonded. Calculating the expansion rate of article (4) is further added. In this case, driving the XY table (2) means driving the XY table (2) in consideration of the expansion rate in addition to the displacement between the two.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, in an embodiment of the wire bonding apparatus according to the present invention, a camera is provided on a bonding head together with an ultrasonic horn.
The bonding head 1 is, as shown in FIG.
It is provided fixed to the XY table 2 that moves in a two-dimensional plane. A bonding apparatus table 3 is provided at a position facing the bonding head 1. The bonding target product 4 is positioned on the surface of the bonding apparatus table 3.

A capillary 7 is supported via an ultrasonic horn 6 on a bonding arm 5 fixed to and extending from the bonding head 1. The capillary 7 is supported on the lower surface of the tip of the ultrasonic horn 6 facing the bonding product 4. The ultrasonic horn 6 applies ultrasonic waves to the capillary 2 in order to perform bonding at a predetermined position of the bonding target product 4 while guiding the wire to the bonding product material 4.

Camera arm 8 fixed to bonding head 1 and extending from bonding head 1 and extending therefrom.
, A camera 9 is supported. The camera 9 includes an imaging objective lens and a CCD forming an imaging surface. An electronic control system 11 is associated with the XY table 2. The electronic control system 11 includes an image processing unit 12, an arithmetic processing unit 13, and a control unit 14. The memory 15 is connected to the arithmetic processing unit 13. Image processing unit 12
Is connected to the arithmetic processing unit 13 and the arithmetic processing unit 1
3 is connected to the control unit 14.

The thermal expansion of the camera arm 8, which is a camera fixing part for fixing the camera, generates a displacement with respect to the origin of the XY table 2. The positional shift causes the camera 9 to shift the field of view. The memory 15 stores conversion data 17 corresponding to the camera-side fixed partial temperature T1 detected by the first temperature sensor 16 attached to the camera arm 8, and outputs the conversion data 17 to the arithmetic processing unit 13. A second temperature sensor 18 is attached to the ultrasonic horn 6. The second temperature sensor 18 detects the ultrasonic horn-side fixed portion temperature T2. The camera-side fixed portion temperature T1 is input to the arithmetic processing unit 13 together with the ultrasonic horn-side fixed portion temperature T2.

The image processing unit 12 converts an image taken by the camera 9 into two-dimensional coordinate data 19 and outputs the two-dimensional coordinate data 19 to the arithmetic processing unit 13. The arithmetic processing unit 13 uses the conversion data 17 to generate the two-dimensional coordinate data 19 based on the camera-side fixed partial temperature T1.
Is corrected by an amount corresponding to the field deviation of the camera 9.

The arithmetic processing unit 13 includes the ultrasonic horn 6
A correction operation for correcting the position of moving the XY table 5 at the time of bonding by converting into a length change due to thermal expansion of the semiconductor device, and the camera 9 recognizes at least two points of each of the semiconductor element and the lead of the bonding target product 4. Based on the position of the target point, a calculation process is performed to correct the thermal expansion of each bonding reference coordinate point stored and held in the memory 9 from the deviation of the coordinate origin and the ratio of the reference length between the target points to the XY table. 2 is transmitted to the control unit 14.

FIG. 2 shows the positional deviation of the camera field of view. The visual field 21 indicated by a solid line is a mechanical coordinate system which is an initial coordinate system (hereinafter, referred to as a reference coordinate system) in which a programmable coordinate system is set in the image processing unit 12 and a specified temperature is set on the programmable coordinate system. The field of view of the camera on the coordinate system, which is indicated by the dotted line 2
Reference numeral 1 ′ indicates a camera field of view when the field of view of the camera fluctuates from the prescribed temperature and the mechanical system expands and contracts to change the field of view of the camera. If the camera arm 8 has thermal expansion, the camera visual field 21 'of the camera 9 shifts to the position shown by the dotted line and moves on the reference coordinate system. The amount of movement is indicated by a displacement / vector 22. Such a displacement / vector 22 can also be obtained by calculation based on the conversion data 17 stored in the memory 15 corresponding to the detected temperature detected by the temperature sensor 16.

FIG. 3 shows a real image of the bonding object (example: semiconductor element) 4 taken by the camera 9. The semiconductor element 4 and the semiconductor wiring board indicated by a solid line are virtual images at a reference position defined on a reference coordinate system. The semiconductor element 4 ′ and the semiconductor wiring board indicated by the dotted line are real images in which the semiconductor element is mounted at a position shifted from the semiconductor wiring board including the rotational component in the die bonding step, and the thermal expansion state is displayed. The target points 24'-1, 24'-2 of the real real image 4 'of the semiconductor substrate device obtained by processing by the image processing unit 12, and the real real image 26 of the bonding lead obtained by processing by the image processing unit 12. '
The actual recognition result (real image position) that is the target point 25′-1 or 25′-2 of the target has the displacement / vector 2 as described above.
2 has a position shift.

The arithmetic processing unit 13 corrects the origin 27 of the bonding coordinates calculated as the midpoint between the target points 24'-1 and 24'-2 of the real image 4 'of the semiconductor device based on the displacement / vector 22. And the distance L + Δ between the target points 24′−1 and 24′−2 of the real real image 4 ′ of the semiconductor element.
By comparing L with the reference distance L, the coefficient of thermal expansion (L + ΔL) / L of the semiconductor element is calculated. On the corrected coordinate system defined by the corrected bonding coordinate origin, the coefficient of thermal expansion (L
Based on (+ ΔL) / L, the position coordinates of the electrode pads of the semiconductor element are corrected by calculation. Arithmetic processing unit 13
Further, based on the temperature detection result of the second temperature sensor 18 attached to the ultrasonic horn 6, the length change due to the thermal expansion of the ultrasonic horn 6 is calculated.

In the corrected coordinate system corrected in this way, a bonding correction position based on the expansion and contraction of the semiconductor substrate as the bonding target product 4 is obtained, and such a bonding correction position is output from the arithmetic processing unit 13. Is input to the control unit 14. The XY table 2 moves based on such a bonding correction position, and the capillary 7 is moved to an appropriate relative position with respect to the bonding target product 4.

FIG. 4 shows the relationship between the two-dimensional coordinate positions of the camera or camera visual field (camera optical axis) based on the temperature change. The temperature detected by the first temperature sensor 16 is from t1 to t.
4, the two-dimensional coordinates (X, Y) of the real image 4 'corresponding to the two-dimensional coordinate position of the camera field of view have a linear relationship in reality.

In the above-described embodiment, an example has been described in which the temperature of the camera mount is detected and converted into the amount of thermal expansion to calculate the amount of displacement of the camera or the objective lens.
An image of the comparative recognition target object obtained by processing the comparative recognition target object by setting an arbitrary comparative recognition target object that is not affected by heat in the movable range of the XY table and imaging the comparative recognition target object with a camera. Before bonding each semiconductor element, an operation of back-calculating the relative shift amount caused by thermal expansion of the holding member of the camera based on the above displacement and correcting the relative position information of the camera and the capillary stored in advance is performed. By creating a control program so as to be automatically executed, it is possible to correct the recognition position deviation due to the thermal expansion of the camera mount at intervals and timing that can be arbitrarily set and changed. The temperature sensor 16 is unnecessary.

As described above, when recognizing at least two target points of each of the semiconductor elements, the recognition position deviation due to the thermal expansion of the camera holding member is eliminated, and the deviation of the coordinate origin from the reference position and the distance between the target points are eliminated. The horn table is driven by correcting the thermal expansion of the horn at the bonding position calculated by correcting the thermal expansion of the bonding coordinate point from the ratio of the reference length to the reference length, and the bonding is performed by driving the XY table. By eliminating the cause of the displacement of the bonding position caused by the thermal deformation (expansion and contraction), the absolute position accuracy of the bonding point can be improved. Compared to conventional wire bonding equipment without means for correcting the thermal expansion of the semiconductor element and the mechanical parts, stable bonding with larger crimped balls to electrode pads of the same dimensions and pitch is possible,
Since the distance between adjacent wirings can be kept constant, semiconductor integrated circuit devices, especially narrow pad pitch bonding (50 μm single row)
m or less), yield and reliability are improved.

[0026]

The wire bonding apparatus and the wire bonding method according to the present invention can realize high-precision bonding.

[Brief description of the drawings]

FIG. 1 is a front view with a circuit block showing an embodiment of a wire bonding apparatus according to the present invention.

FIG. 2 is a geometrical diagram showing a camera's field of view shift.

FIG. 3 is a geometric diagram illustrating correction of a coordinate system.

FIG. 4 is a graph showing the linearity of coordinates.

[Explanation of symbols]

2 XY table 3 Fixed table 4 Bonding object 5 Second holder 7 Capillary 8 First holder 9 Camera 14 Driving amount calculation unit 16 Temperature detector (first temperature detector) 18 ... 2nd temperature detectors 24-1 and 24-2, or 25-1 and 25-22 ... 2
Points 24'-1 and 24'-2, or 25'-1 and 25'-
22 ... 2 points L ... Standard length

Claims (8)

[Claims] An XY table; a first holder supported by the XY table; a camera held by the first holder; a second holder supported by the XY table; A capillary held by the holding body, a fixing base for fixing a bonding object, a position displacement of the camera caused by a temperature change of the first holding body with respect to the origin of the XY table, and And a driving amount calculation unit for calculating a driving amount of the XY table based on a displacement of the capillary caused by a temperature change of the second holder. 2. The method according to claim 1, further comprising an expansion rate calculation unit configured to calculate an expansion rate of the bonding target product, wherein the drive amount calculation unit calculates a displacement of the bonding point of the bonding target product with respect to the fixed base based on the expansion rate. 2. The wire bonding apparatus according to claim 1, wherein the calculation is performed in consideration of a positional displacement of a camera and a positional displacement of the capillary. 3. The wire bonding apparatus according to claim 2, wherein the expansion coefficient is calculated based on a reference length of two points of the article to be bonded and a current length of the two points at a current time. 4. The apparatus according to claim 1, further comprising a temperature detector configured to detect a temperature of the second holder, wherein the driving amount calculating unit calculates the position displacement of the capillary based on the temperature. The wire bonding apparatus according to claim 1. 5. A first detecting means for detecting a first temperature of the first holder.
A temperature detector; and a second temperature detector for detecting a second temperature of the second holder, wherein the drive amount calculation unit calculates the position displacement of the camera based on the first temperature. And calculating the displacement of the capillary based on the second temperature.
Wire bonding equipment. 6. An expansion rate calculation unit for calculating an expansion rate of the bonding target product, wherein the drive amount calculation unit calculates a displacement of a bonding point of the bonding target product with respect to the fixed base based on the expansion rate. 6. The wire bonding apparatus according to claim 5, wherein the calculation is performed in consideration of the difference. 7. The method according to claim 7, wherein the XY table is driven to
Moving a camera supported by a first holder supported by a Y table with respect to an object to be bonded; driving the XY table to support a capillary supported by a second holder supported by the XY table; Is moved with respect to the object to be bonded. By imaging the object to be bonded by the camera, the object to be bonded generated due to thermal fluctuation of the first holder in a coordinate system defined by the camera Calculating a first misalignment of an article; calculating a second misalignment of the capillary caused by thermal fluctuations of the second holder; based on the first misalignment and the second misalignment And driving the XY table. 8. The expansion rate of the bonding target product is calculated by calculating the distance between two points of the bonding target product in a coordinate system defined by the camera by imaging the bonding target product by the camera. 8. The wire bonding according to claim 7, further comprising calculating, wherein driving the XY table includes driving the XY table in consideration of the expansion rate in addition to the first position shift and the second position shift. Method.